First I assume "crc coating" is chromium carbide/nickel chromium coating.

I don't know what is typically required for combustion parts, but typical Ra roughness capabilities for these coatings lies somewhere between 0.1 - 0.6 micrometres for grinding with possibility of getting down to ~0.05 with lapping/super-finishing. Obviously, this is very dependent on process parameters, materials and grinding procedures.

First I assume "crc coating" is chromium carbide/nickel chromium coating.

I don't know what is typically required for combustion parts, but typical Ra roughness capabilities for these coatings lies somewhere between 0.1 - 0.6 micrometres for grinding with possibility of getting down to ~0.05 with lapping/super-finishing. Obviously, this is very dependent on process parameters, materials and grinding procedures.

First I assume "crc coating" is chromium carbide/nickel chromium coating.

I don't know what is typically required for combustion parts, but typical Ra roughness capabilities for these coatings lies somewhere between 0.1 - 0.6 micrometres for grinding with possibility of getting down to ~0.05 with lapping/super-finishing. Obviously, this is very dependent on process parameters, materials and grinding procedures.